离心萃取法卤水提硼的研究

以青海省东台吉乃尔盐湖酸化提硼母液为原料,采用CTL50-N型小流量环隙式离心萃取器,以异辛醇/磺化煤油为萃取体系萃取析硼母液中的硼。讨论了萃取剂浓度、萃取酸度、相比、流速、转速及萃取级数对萃取工艺的影响。试验结果表明,在最佳工艺参数的条件下其萃取率达到了97%以上,反萃取率在98%以上,通过酸性溶液可使硼酸浓缩到47g/L。本试验将为产业化提硼提供依据,离心萃取器在这一方面也将会有广泛的应用前景。     

原状非饱和Q3黄土的土压力原位测试和强度特性研究

为了揭示原状黄土的土压力的分布规律及其在开挖过程和浸水过程中的变化规律,对兰州市一个高18 m的Q3黄土边坡进行了现场试验,量测了边坡的位移、土压力、基质吸力和含水率,观测了该边坡的破坏过程,同时进行了一组控制吸力的原状黄土的非饱和三轴剪切试验。研究结果表明：①原状Q3黄土的表观黏聚力和有效摩擦角与吸力之间均为非线性关系。②原状黄土边坡的土压力随着土坡开挖深度的增加而不断增大。边坡开挖结束后的土压力分布大致呈中间大,两端小的三角形,最大土压力位置在大约坡高的1/3位置处。与朗肯土压力理论计算结果相比,实测黄土边坡的土压力远小于计算值。在浸水条件下,非饱和黄土的边坡土压力增速较大,浸水是边坡产生破坏的直接原因。     

Q3黄土侧向卸荷时的细观结构演化及强度特性

利用应力控制式CT-三轴仪,在控制吸力的条件下研究了原状Q3黄土的细观结构演化和强度特性。结果表明：侧向卸载时,非饱和Q3黄土的应力-应变关系呈硬化型,可用双曲线描述;利用CT数据与试验中所施加偏应力之间的关系可确定试样的屈服应力,屈服应力随着吸力和固结净围压的增大而增大;侧向卸荷剪切试验结果得到的强度参数低于常规三轴压缩剪切试验的结果;利用定义的非饱和Q3黄土的结构参数,建立了侧向卸载过程的细观结构演化方程。     

非饱和土抗剪强度及土压力统一解

基于统一强度理论和非饱和土双应力状态变量抗剪强度,合理考虑中间主应力效应,建立了非饱和土双应力状态变量抗剪强度统一解,并与文献试验结果进行比较,验证了公式的正确性;进而考虑基质吸力的不同分布,得到非饱和土主动土压力和被动土压力统一解,克服了朗肯土压力的不足,并得出中间主应力和基质吸力对土压力的影响特性。研究结果表明,主动土压力随着统一强度理论参数和基质吸力的增大而不断减小,被动土压力则相反;当基质吸力沿深度线性减小时,主动土压力和被动土压力都不像基质吸力沿深度为常数时变化得那么快。该结果为非饱和土抗剪强度和土压力分析提供了理论依据,对工程设计有一定的参考价值。     

北海酸雨区的成因简析

北海市的空气质量指数一直为优,可是从北海近几年的酸雨观测结果表明,北海属于酸雨地区,究其原因主要是由于雷暴造成。     

Identifying outliers and assessing the accuracy of amino acid racemization measurements for geochronology: I. Age calibration curves

Numerical ages derived from amino acid racemization (AAR) geochronology are typically based on calibration curves that relate the extent of AAR to the age of independently dated specimens. Here, we compare options for developing calibration curves and quantifying age uncertainties using AAR data from 481 late Holocene shells, and AMS ¹⁴C analyses of 36 shells of four molluscan taxa (Ethalia, Natica, Tellina, and Turbo) collected from shallow sediment cores from a back-reef lagoon of the central Great Barrier Reef. The four taxa differed substantially in the quality of their geochronogical results. Explicitly including data from specimens alive at the time of collection improves calibration curves, but weighting numerical ages based on their uncertainty has no effect. Calibration curve statistics do not adequately assess calibration uncertainty. The relation between ages inferred from different amino acids is recommended for identifying aberrant specimens and quantifying the uncertainty of inferred ages. For this study, the AAR ages based on two amino acids (aspartic acid and glutamic acid) exceed 200 yr or 20% of their mean inferred age in 15% of the specimens. Once these were removed, the mean age error (1σ) for individual specimens based on two amino acids analyzed in duplicate subsamples ranged from 53 to 142 yr for Tellina and Turbo, respectively, or about a 30% age error for these relatively young shells. This compares favorably with analytical errors estimated at 50 yr or 5%. The presence of notable outliers undetectable using data from single amino acids emphasizes the importance of analyzing multiple amino acids.     

非饱和土热力学参数确定的探讨

研究非饱和土热力学的力学性质,必须建立能量守恒方程,表征能量的两个基本物理力学参数（体积比热系数和热传导系数）的确定是求解能量守恒方程的重要因素。对于不同颗粒组成的土体,对其干燥颗粒有效热力学参数进行了分析,对固体、液体和气体三相共存的热力学参数进行了研究,并对计算结果进行了对比分析,在此基础上,提出了较适合计算热传导系数的方法,并将此方法和体积平均法、自洽法及Hashin-Strikman方法进行了比较。经与试验结果对比表明：提出的方法能较好地描述非饱和土的热力学参数特性。     

球形颗粒紧密堆积状态时的吸力分析

根据圆液面假设和热力学基本原理,研究了球形颗粒紧密堆积模式在水封闭状态（状态2）时的吸力特性,得到了状态2中3类吸力和3类等效吸力与饱和度的定量关系和以接触角和饱和度或饱和半径为参数的吸力比表达式。进一步的研究表明,在状态2中吸力比都小于1,与基于松散堆积模式在水封闭状态（状态1）时得到的结果比较后可知,随着颗粒排列密实度的增大,相对于基质吸力,张力吸力的作用将有所降低但仍然不可忽视。另外,随饱和度变化,状态2中的3类吸力,特别是3类等效吸力的变化趋势与基于状态1得到的结论基本一致。在状态2中,对数吸力比与饱和半径呈明显的线性关系,吸力比与饱和度也呈明显的线性关系,前者与状态1中的吸力演化规律一致,而后者则存在较大不同。     

Determination of experimentally enriched15N in nitrate nitrogen based on an improved method of azo dye formation

A method has been developed for determination of¹⁵N isotope ratio in nitrate nitrogen, which is a major analytical step in tracer experiments for studies of nitrate metabolism in the marine environment. The method is based on diazotization of nitrite with sulfanilic acid following reduction of nitrate to nitrite by a cadmium-copper column. The diazonium compound is then subject to the azo coupling reaction with 2-naphthol, and the azo dye formed is extracted by a solid phase extraction column. The dye eluted from the column is collected, and total nitrogen and¹⁵N content of the dye are determined by mass spectrometry. Sulfanilic acid can also remove preexisting nitrite by heating the sample under acidic conditions before passing through the cadmium-copper reduction column. The average recovery of nitrate nitrogen was 86%. A procedure for reducing the background nitrogen that derives from the analytical operations has been developed; background nitrogen was limited to about 0.25 μg-atomN. The variation in the background nitrogen levels reflects the range of error in¹⁵N determination of nitrate nitrogen by this method. Application of the present method to a¹⁵NO₃ ⁻ isotope dilution experiment for determination of nitrification rate in sea water is demonstrated.     

Production of Domoic Acid by Pseudo-nitzschia multiseries Hasle, Affected by Lithium

Abstract. Upon enrichment with lithium 385.6 μM Li, culture of Pseudo-nitzschia multiseries H asle produces substantially higher level of the neurotoxin domoic acid DA 230 fg · cell^-1 than the control 135 fg · cell^-1. We hypothesize that in Cardigan Bay, where the first domoic acid episode was reported, high levels of Li could have originated via a massive freshwater run-off involving an adjacent dump. Lithium enrichment may have played a part in enhancing DA production leading to the intoxication episodes of 1987. Thus, anthropogenic activities may play a role as a sustainer of algal blooms and should be included in habitat management considerations involving coastal and inshore algal blooms, both toxigenic and non-toxigenic.